Hydraulic circuit for saw mill feed works



Oct. 27, 1959 J. R. sTocKETT HYDRAULIC CIRCUIT FCR sAw MILL FEED woRxs Filed Aug. 29, 1958 ATTORNEY UnitedStates Patent O HYDRAULIC CIRCUIT FOR SAW MILL FEED woRKs James Roy Stockett, Tulia, Tex. Application August 29, 1958, Serial No. 758,132 2 Claims. (Cl. 6051) proved circuit hookup for the hydraulic actuation of a sawmill feed carriage.

Another object is to provide a hydraulic control circuit for a saw mill Vfeed works which can effect a smooth stopping and starting of the carriage and at the same time provide rapid traverse returning of the carriage at high speed and with great eiciency.

Still another object is to provide'a feed, rapid traverse reversing and stop control 'circuit requiring a minimum of eiort and skill on the part of the operator of the saw mill.

It is also an important object of this invention to utilize the initial weight of the massive saw mill carriage to regain a large amount ,of uid volume and pressure through a novel check valve arrangement in the circuit when Ithe carriage is stopped at each end of the stroke.

A further object of this invention is to utilize the piston and cylinder of the saw mill carriage as a hydraulic pump as the saw mill carriage is stopped at the end of each stroke so as to pump fluid into an yaccumulator through a novel check valve arrangement to effect a smooth stopping of the carriage regardless of the manner in which the operator may manipulate the control lever when he moves the lever from the feed position to the stop position, or on over to the reverse position.

And still another object is to provide `the above recited hydraulic circuit with critically positioned check valve therein so that the saw mill carriage will stop smoothly against the cushion of air in ythe Aaccumulator so there will be no sudden jerk or shock when the control lever is manipulated in any manner.

And nally it is the object of this invention to provide a novel hydraulic circuit for a saw mill feed works which utilizes the inertia of the saw mill carriage for recovery of pressure and energy while Iat the same time effecting a smooth stopping of the carriage at the end of each stroke.

Further features and advantages of this invention will appear from a detailed description of the drawings in which:

The drawing is a diagram showing the hydraulic circuit for a saw mill feed Works incorporating the features of this invention.

As an example of one embodiment of this invention there is shown a hydraulic control circuit including a uid reservoir containing a suitable hydraulic lluid at the fluid level 11. immersed in the fluid in. the reservoir 10 is a control valve 12 having a valve body 13 in which is formed a bore having a series of axially spaced surfaces 14, 15, 16 and 17 separated by annular grooves 18, 19 and 20. A valve spool 21 consists of the axially spaced bearing portions 22, 23 and 24 interconnected by reduced portions 25 and 26 formed integral with the bearing portions 22, 23 and 24. An operating handle 27 is suit- 2,909,897. -Patented Oct. 27, 1959 ice 2 ably mounted on a supporting pivot pin 28 and is pivotally connected by a pin 29 to the outer end of the stem 30 connected to the valve spool 211 so that by appropriately manipulating the handle 27 the valve spool may be axially reciprocated in the valve body 13.

A uid pressure pump 31 having a suction line 32 receiving a supply of fluid from the reservoir 10 discharges lluid under pressure through the line 33 into the annular groove 19 in the valve body 13, a suitable pressure relief Vvalve 34 being connected through line 35 into line 33 yand discharging through line 36 into the reservoir ,10 to prevent overloading the pump 31. An air pres.- sure accumulator 37 having an air chamberl 38 above the fluid 39 in the bottom portion of the accumulator is connected at its lower end 40' by'a line 41 to the annular groove 19 in the valve body 13 so that uid pressure from the pump 31 through line 33 is always connected to line 41 and the accumulator 37.

A uid pressure cylinder 42 has a piston 43 and a piston rod 44 connected in a suitable manner to a saw mill carriage 45 for reciprocation thereof by controlling the application of iluid pressure in the cylinder 42. One

y:end of cylinder 42 is connected by la line 46 tothe iannular groove 18 of the valve body 13 while the other 'line41 whileline 47 is connected'through' a check valve 49 for free ow into the line 41. Free flow from suction line 50 and check valve 51 into line 46 is provided, While free flow from suction line 52 and check valve 53 into line 47 is also provided, both suction lines 50 and 52 receiving a supply of duid from the reservoir 10.

In operation: When the operating handle 27 is moved to Stop position, bearing portion 23 of valve spool 2.1 closes annular groove 19 so that the pump 31 builds up pressure in the accumulator 37 to the setting of the relief valve 34. At this time the open ends of the bore surfaces 14 and 17 are closed by the respective bearing portions 22 and 24 of the valve spool 21 so as to lock fluid in both ends of the cylinder 42 to bring the carriage 45 to a stop. Check valves 51 and 53 are normally closed at this time and the check valves 48 and 49 are held closed by pressure in line 41.

When the operating handle is moved to Forward position, annular grooves 18 and 19 .are interconnected so that pressure from both the pump 31 and line 41 from the accumulator is applied in line 46 to forwardly actuate the piston 43, check valve51 being normally closed, and check valve 48 being held closed or floating against pressure inline 41. The other line 47 of the cylinder at this time exhausts out through bore surface 17 back to reservoir 10, check valve 53 being normally closed, and check valve 49 being held closed by pressure from line 41. Thus rapid forward movement is effective for the carriage 45.

As the operating handle 27 is returned toward Stop position the inertial coast of the heavy carriage 45, causes a suction in line 46 greater than the supply from the annular groove 18 now partially cut off from annular groove 19 but this is automatically relieved by suction through the check valve 51 thus preventing suction spring back as the carriage is brought to a Stop. Also, fluid escaping from line 47 of the cylinder under these conditions when restrained from free escape through the bore surface 17 is also relieved by passagethrough check valve 49 to help again build up pressure in the accumulator 37 for the next return travel of the carriage in reverse direction, check valve 53 being normally closed at this time. Obviously the same operatori occurs with the operating handle moved to Reverse position and v3 return, with the appropriate check valves operating as indicated.

By appropriately operating the handle and modulating the position of the valve spool 21 a nicety of smooth and accurate control of the carriage movement canbe obtained with accurate, smooth stopping and starting from one reversal to another.

While the apparatus herein disclosed and described constitutes a preferred form of the invention, it is also to be understood that the apparatus is capable of mechanical alteration without departing from the spirit of the invention and that such mechanical arrangement and commercial adaptation as fall within the scope of the appendent claims are intended to be included herein.

Having thus fully set forth and described this invention, what is claimed and desired to lbe obtained by United States Letters Patent is:

l'. In combination in a hydraulic circuit for operating the carriage of a saw mill feed works, a fluid reservoir, a control valve having a valve body, a valve spool reciprocatable in said valve body including means for manually actuating said valve spool, an annular groove in said Valve body, a fluid pressure pump receiving a supply of fluid from said reservoir connected to supply fluid under pressure to said annular groove, an accumulator connected to said annular groove, a uid pressure cylinder having a piston and piston rod connected to actuate said carriage, a second annular groove in said valve body connected to one end of said cylinder, a third annular groove in said valve connected to the other end of said cylinder, a check valve connected between said rst mentioned annular groove and said second annular groove for free ow between said second annular groove and said first mentioned annular groove, a check valve connected between said first mentioned annular groove and said third annular groove for free ow between said third annular groove and said rst mentioned `annular groove, a check valve connected between said reservoir and said second annular groove for free low from said reservoir to said second annular groove, a check valve connected between said reservoir and said third annular groove for free ilow from said reservoir to said third annular groove, and means on said valve spool when moved -to intermediate stop position toy close o: said first mentioned annular groove so that said pump is connected solely to said accumulator while said second and third annular grooves are blocked by said valve spool.

2. In a hydraulic circuit as set forth in claim l wherein said last mentioned means further includes an arrangement wherein said rst mentioned annular groove may be connected to one and the other of said second and third annular grooves while the other of said second and third annular grooves are connected to discharge into said reservoir by the manipulation of said operating handle.

Stockett v Ian. 22, 1957 Ball Aug. 13, 1957 

